Motion transformers for electronically controlled timepiece



Feb. 2, 1965 M. HETZEL 3,167,905 MOTION TRANSFORMERS FOR ELECTRONICALLYCONTROLLED TIMEPIECE Filed July 16, 1965 ELscflfO'y/c INVENTOR. MAX#Erza United States Patent Otlice 3,157,905 Patented Feb. 2, 19653,167,905 MOTIGN TRANSFGRMERS FOR ELECTRONI- CALLY CONTROLLED TEMEPIECEMax Hetzel, New Hyde Park, N.Y., assignor to Bulova Watch Company, IIIQ,New York, N.Y., a corporation of New York Filed July 16, 1963, Ser. No.295,406 1 Claim. (Ci. 5823) This invention relates generally toelectronically controlled timepieces which incorporateelectromagnetically actuated tuning forks, and more particularly toimproved motion transformers for converting the reciprocating movementof the tuning fork into rotary motion for driving the gear train of thetimepiece.

In ordinary electric watches, make-and-break contacts are mechanicallyoperated by the oscillation of the balance Wheel. Each time thesecontacts close, battery current flows in a coil to electromagneticallyimpulse the balance Wheel. Such mechanically operated make-and-breakcontact systems are subject to wear as well as to deterioration andcontamination of the delicate contact points which must open and closean electric circuit without fail 216,000 times a day. The slightestsparking will cause rapid deterioration of these contacts and earlyfailure of the watch.

In my United States Patents 2,971,323; 3,070,951; 2,960,817; 3,057,147;2,949,727; 2,929,196; 2,908,174; 2,900,786, and 2,888,582, I disclose anelectronically controlled timepiece which does away with a balance wheeland escapement, as well as with make-and-break contacts. My timepieceemploys a self-suificient timekeeping standard formed by a tuning forkwhose vibratory motion is sustained electromagnetically by abattery-energized transistor circuit. This motion is transmitted to arotary movement including the usual gear train and dial pointers bymeans of an index finger attached to one tine of the fork, the fingeradvancing a ratchet or index wheel which drives the gear train.

In the co-pending application of Bennett et 211., Serial No. 89,896,filed January 16, 1961, now abandoned, there is disclosed a motiontransformer for a timepiece of the type described in my patents, thetransformer including a jewel-tipped index finger which engages theteeth of an index or ratchet wheel so that the oscillations of the tinetransmit turning impulses to the wheel. Operating in conjunction withthe index wheel is a pawl whose design is similar to that of the indexfinger, the pawl being pivotally attached to the pillar plate of thetimepiece. The index finger and pawl are both tensioned downwardly suchthat when the timer is retracted by the tine, the resultant reversetorque produces a backup which is arrested by the pawl, the pawl beingphased several teeth plus onehalf tooth from the finger and beingpositioned in advance thereof, in the direction of wheel rotation.

One important problem which arises in a ratchet system of the typedisclosed in said co-pending application, is with respect to the phaserelationship between the pawl and the index finger. While thisrelationship may be initially adjusted to a desired fixed value, it maybe upset by the twisting of the pillar plate on which the pawl ismounted. Any deviation from this phase relationshi lowers the stroberange and impairs the reliability and operation of the ratchet system.Twisting of the pillar plate frequently occurs when inserting andclamping the watch movement in a watch casing.

Accordingly, it is the principal object of tits invention to provide amotion transformer in which the phase relationship between the ratchetwheel and the drive elements therefor is maintained constant, regardlessof twisting of the pillar plate.

More specifically, it is an object of the invention to provide a motiontransformer for a tuning-fork timepiece wherein an index wheel is drivenby a pair of push-pull actuated index fingers attached to the respectivetines of the fork.

Still another object of the invention is to provide a motion transformerfor a tuning fork timepiece wherein the index wheel is driven in onedirection by an index finger secured to one tine of the tuning fork,reverse movement of the wheel being prevented by a pawl secured to astationary portion of the tuning-fork, whereby twisting of the pillarplate has no influence on the phase relationship of the pawl and finger.

For a better understanding of the invention as well as other objects andfurther features thereof, reference is made to the following detaileddescription to be read in conjunction with the accompanying drawingwherein like components in the several figures are identified by likereference numerals.

In the drawing:

FIG. 1 is a schematic representation, in perspective, of the basiccomponents of an electronic timepiece including a motion transformer inaccordance with the invention;

FIG. 2 shows another preferred embodiment of a motion transformer inaccordance with the invention; and

FIG. 3 shows a push-pull drive system in accordance with the invention.

Referring now to the drawing. the major components of a timepiece inaccordance with the invention are a time-keeping standard constituted bya tuning fork 10 and an electronic drive circuit 11 therefor, a rotarymovement of conventional design including a gear train 12 for turningthe hands of the timepiece, and a motion transformer including an indexwheel 13 operatively intercoupling the fork it and the rotary movement12 and acting to convert the vibratory action of the fork into rotarymotion.

All of the electrical components of the drive circuit are mounted onsub-assembly units or modules attached to a disc-shaped metallic pillarplate 14 which may be supported within a watch casing of standard designor within any other type of housing, depending on the use to which thetimepiece is put.

Tuning fork 10 is provided with a pair of flexible tines l5 and 15 whosefeet are interconnected by a relatively inflexible base 17, the basebeing provided with an upwardly extending stem 18 secured to the pillarplate by suitable screws 19 and 20. The central area of the pillar plateis cut out to permit unobstructed vibration of the tine The tuning forkis actuated by means of a first transducer T constituted by a magneticelement 21 secured to the free end of tine 15, the element coacting witha drive coil 22, and a phase sensing coil 23. Drive coil 22 is wound onan open-ended tubular carrier 24 amxed to a sub-assembly mounting form Fwhich is secured to pillar plate 14. Coils 22 and 23 may be wound injuxtaposed relation on carrier 24 or the phase sensing coil 23 may bewound over drive coil 22.

A second transducer T is provided, constituted by a magnetic element 25secured to the free end of tine 16 and coacting with a drive coil 26wound on a tubular carrier 27.

The electronic drive circuit 11 of the tuning fork comprises atransistor 23, a single-cell battery 29, and an RC biasing networkconstituted by a condenser 30 shunted by a resistor 31. Transistor 28 isprovided with base, emitter and collector electrodes represented byletters B, E and C, respectively.

The base electrode is coupled through the R-C bias network 40-41 to oneend of the phase-sensing coil 23, the other end of the coil beingconnected to one end of the drive coil section 22. The drive coil 26 isconnected in a series with drive coil 22 to the collector electrode C ofthe transistor.

The emitter electrode E is connected to the positive terminal of thebattery 29, the negative terminal thereof being connected to thejunction of drive coil 22 and phasesensing coil 23. Thus the battery isconnected serially through both drive coils 22 and 26 between theemitter and collector electrodes of the transistor, the collector beingnegative relative to the emitter.

The transistor is preferably of the germanium junction type, and thepolarity of the battery connection is shown as it exists when thetransistor is of the PNP type. Obviously for other types of junction andpoint contact transistors made of such materials as silicon orgermanium, the battery connections are arranged in accordance with theparticular requirements.

The interaction of the electronic drive circuit and the tuning fork isself-regulating and functions not only to cause the tines to oscillateat their natural frequency, but also to maintain oscillation at asubstantially constant amplitude. In practice, the amplitude ofoscillation of the tines will be maintained at a substantially constantvalue or quickly returned to this value in the event of a mechanicaldisturbance. The electrical behavior of this circuit is set out morefully in the above-identified patents.

A tuning fork is a high Q mechanical oscillator and will vibrate at anatural frequency determined by the dimensions of the tines and theloading thereon which, in this instance, is determined by the mass ofmagnetic elements attached to the free ends. The rate at which thetimepiece movement is driven is directly proportional to the operatingfrequency of the vibrator, so that the accuracy of the timepiece may beregulated by predetermining the operative frequency of the tuning fork.In practice, a fork vibrating at 360 cycles per second may be used.

The vibratory motion of the tuning fork is converted by a motiontransformer into rotary motion. This transformer is constituted by aratchet and pawl mechanism operated by the tuning fork to drive indexwheel 13. The index wheel 13 acts as the actuator for the rotarymovement 12 and it is therefore essential that this wheel be advanced bythe vibratory fork at a constant rate. This is effected by means of anindex finger 32 which is soldered or otherwise attached to a post 33secured at one end to time 16, post 33 having a constriction therein toprovide a bending neck.

The index finger is in the form of a light leaf spring, and carries atip which may be a precious or semiprecious stone, such as sapphire. Thetip engages the teeth of index wheel 13 so that the oscillations of thetine transmit turning impulses to the wheel. The shaft of the wheel 13is provided with a pinion which intermeshes with the first gear in thegear train 12.

Operating in conjunction with the index wheel 13 is a pawl 34 whosedesign is similar to that of the index finger, the pawl being attachedto a post 35 mounted on a bracket 36 secured to stem 18 intermediatescrews 19 and 26. The index finger and pawl are both tensioneddownwardly, the jewelled tips thereof being parallel with the teeth ofthe index wheel. The tension is such that when the finger is retracted,there is suificient reverse torque to cause the wheel to reversedirection. This backup, however, is arrested by pawl 34, which is phasedseveral teeth plus one-half tooth from the finger and is positioned inadvance thereof in the direction of wheel rotation.

The necessary phase adjustment between the finger and pawl can beeffected by pivoting the ratchet wheel with its bearings around thecenter of the first gear train wheel, or by pivoting bracket plate 36,so that this adjustment can be made. In either case, the phaseadjustment, once made, will be maintained, for the relationship is notdistorted by twisting of the pillar plate, the pawl being independent ofthe pillar plate and being connected to a rigid portion of the fork.

In the modification shown in FIG. 2, a similar result may beaccomplished by a fork structure mounted on the pillar plate by a baseextension 17a connected to the base 17 by a yieldable neck portion 1712,the fork being provided also with an upwardly extending, non-vibratingstem 18a. The stem 13a is inclined toward tine 16, and the pawl 34 ismounted thereon rather than on the pillar plate, thereby shortening thelength of the pawl. Thus in the embodiments of FIGS. 1 and 2, the pawlposition relative to the index finger is not aifected by twisting of thepillar plate, for the pawl and finger are both mounted on the fork.

Instead of having a ratchet finger fixed on one tine of the fork and apawl fixed on the pillar plate or on a non-vibratory portion of thefork, it is possible, as shown in FIG. 3, to do away with the pawlentirely and to drive the ratchet wheel 13 in a push-pull manner. Thisis accomplished by two index fingers 36 and 37, each fixed to one tineof a tuning fork so that the fingers vibrate at the same amplitude andfrequency in opposing phase. The angle alpha (or) between the two fingerdirections is equal to the angle between the two radii going through thecenter of the ratchet wheel and the jewelled tips of the fingers. Thislast condition is necessary to ensure that the jewels lie flat on theratchet wheel teeth.

For the same ratchet wheel, the amplitude of one finger need be onlyhalf as large as it is for the ratchet and pawl system. With thispush-pull system, the inertia power will be only one-fourth of theratchet and pawl system, but since there are twice as many strokes, thetotal lost power is one-half that of the ratchet and pawl system. Inefiect, therefore, the ratchet wheel appears to have only half thethickness of the wheel in the ratchet and pawl system. Obviously,twisting of the pillar plate has no influence on the phase relationshipof both jewels when these jewels engage the wheel at closely spacedpoints. Because both fingers are mounted on the tuning fork, movement ofthe wheel axle with respect to the foot of the fork does notsignificantly change the phase between fingers.

The fork construction shown in FIG. 1 does not lend itself to push-pulloperation of the ratchet wheel, in that the fork tine separation is toogreat, as a result of which the length of one finger is far in excess ofthe other, and it is not possible to run the fingers in almost parallelpaths. In order to facilitate a push-pull drive, theelectromagnetically-operated fork in FIG. 3 is composed of two closelyspaced tines 38 and 39 whose feet are joined to a base support 40mounted on the pillar plate of the timepiece, the base running parallelto the tines. In this way, the two fingers 36 and 37 connected to thebase 49 extend in substantially parallel paths to the wheel 13. Similarresults may be obtained with S or Z-shaped forks, or other symmetricalor asymmetrical configuratrons, which make it possible to extend indexfingers of substantially the same length to an index wheel to effectpush-pull operation thereof.

While there have been shown preferred embodiments of motion transformersin accordance with the invention, it will be appreciated that manychanges and modifications may be made therein without, however,departing from the essential spirit of the invention as defined in theannexed claim.

What is claimed is:

A timepiece comprising:

(A) a gear train for turning the hands of the time piece,

(B) a tuning fork having a pair of vibrating tines attached at theirroots to a yoke and extending upwardly therefrom and a mounting baselying to one side of said tines, said base being attached at one 5 6 endto said yoke and extending upwardly therefrom, References Cited by theExaminer said tines being closely ad acent each other, FOREIGN PATENTSC) means sustalmng said tines 1n vibration, (D) and a motion transformerfor converting the vi 579,293 7/ 24 Francebrations of the tines intorotary motion for driving said gear train, said transformer including aratchet wheel coupled to said train and a pair of fingers ofsubstantially the same length attached to the re- LEO SMILOW PrimaryExaminer spective tines and engaging said wheel at different pointsthereon to drive same in double-acting rela- 10 JOSEPH P. STRIZAK,Examiner. tion.

5 (Note-The specification pages are numbered 576,298

except for page 2 which carries No. 570,298.)

